This invention relates to an apparatus for finishing lenses. More specifically, this invention related to an apparatus for polishing or fining toric surfaces of ophthalmic lenses. In ophthalmic lens finishing, the terms "polish" and "fine" are terms of art indicating a degree of finish achieved. Since the subject apparatus is used for both polishing and fining the terms will be used interchangeably.
In ophthalmic optics, lens blanks are formed from glass or plastic and a convex surface of the lens is mounted upon a retaining member known as a lens block. The lens and block are then accurately mounted upon a grinding apparatus wherein a torodial surface of compound prescriptive value is rough ground into a concave portion of the lens. In this regard a first principal meridian of the lens typically has a different dimension than a second principal meridian normal to the first. Following the initial grinding operation, an ophthalmic lens is fined and then polished to a final prescriptive value. Left and right lenses are then mounted upon an edge grinding machine to cut the outer peripheral shape required to be compatible with an ultimate wearers eye glass frame.
The subject invention is directed to a polisher-finer apparatus and comprises an improvement over a Stith U.S. Pat. No. 3,732,647 of common assignment with the subject application. More specifically, the Stith patent discloses a polisher-finer wherein the lens is finished by being biased into a lapping tool having a toric surface of the final desired prescriptive value. The lapping tool is driven in an orbital, break-up motion relative to the lens to prevent ridges, grooves and/or other aberrations from forming in the lens surface which might occur if regular or uniform motion devices were utilized. In addition to orbital, break-up motion of the lapping tool the Stith patent discloses moving the lens in a transverse motion from side-to-side. In at least one other system, front to rear motion is added to the transverse motion of the lens to be finished.
Although polisher-finer systems of the type previously described have been widely utilized, room for significant improvement remains. In this regard, it would be desirable to increase the relative speed of motion between the lapping tool and lens without sacrificing any of the system finishing ability. Still further it would be desirable to be able to facilely vary the amplitude of the orbital, break-up motion of the apparatus.